Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture kinetic energy from wind using known foil principles and transmit the kinetic energy through rotational energy to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
Wind turbine rotor blades generally include a body shell formed by two shell halves of a composite laminate material. The shell halves are generally manufactured using molding processes and then coupled together along the corresponding edges of the rotor blade. In general, the body shell is relatively lightweight and has structural properties (e.g., stiffness, buckling resistance and strength) which are not configured to withstand the bending moments and other loads exerted on the rotor bade during operation. To increase the stiffness, buckling resistance and strength of the rotor blade, the body shell is typically reinforced using spar caps that engage the inner surfaces of the shell halves. The spar caps may be constructed of various materials, including but not limited to glass fiber laminate composites and/or carbon fiber laminate composites.
During the life of the wind turbine, the rotor blades are particularly prone to lightning strikes. Thus, modern wind turbines typically include a lightning protection system having one or more lightning receptors disposed on the exterior of the rotor blades and a lightning conductor or cable wire coupled to the lightning receptor(s) and extending through the rotor blades from a blade tip to a blade root and through other components until grounded down through the tower to a ground location. Accordingly, when lightning strikes the rotor blade, the electrical current may flow through the lightning receptor(s) and may be conducted through the lightning system to the ground. However, when a lightning strike occurs, unwanted discharges may arise from the spar caps to the body shell, which may cause significant damage to the rotor blade.
Accordingly, there is a need for a spar cap design that prevents such unwanted discharges from the spar caps. More specifically, a spar cap constructed with alternating layers of conductive material so as to electrically connect the layers of the spar cap to the lightning protection system would be welcomed in the art.